28 Mr. H. J. Carter on the 



of the former (that is, in Stellispongia) is short, cylindrical, 

 and obtuse ; but this seems to arise from the pointed ends in 

 most instances being hidden beneath the undulations. In Stel- 

 lispongia variabilis, from the Upper Keuper of St. Cassian in 

 the Tyrol, the spicules appear to have consisted of about two 

 bends, and to have been about 18 by 2-6000ths, and in Phare- 

 trospongia Strahani, from the Greensand of Folkstone, where 

 the spicule is simply curved, about 66 by 2|-6000ths inch in 

 their greatest dimensions respectively. I am indebted to Dr. 

 Steinmann, of Strassburg, who has published a good photo- 

 graph of it (No. 13, Taf. ix. fig. 2), for the preparation of the 

 former, and to Prof. Sollas for an entire specimen of the latter, 

 which is thoroughly described and illustrated in the c Quarterly 

 Journal of the Geological Society 7 (No. 5, p. 242 &c, 

 pi. xi.), both of which I have had by me for some years past. 



Having stated above that neither the spicular form in 

 Stellispongia nor that in Pharetrospongia bears the u least 

 resemblance " to that of existing Calcisponges, I of course 

 mean in the absence of tri- and quadriradiates ; but, to prevent 

 cavilling, I would add that in only one or two instances among 

 existing Calcispongise is there a distinct resemblance to the 

 monactinellid spicule of Pharetrospongia Strahani, and in 

 these they are subsidiary — that is, in great minority. Thus 

 they are scattered horizontally over the surface and throughout 

 the body, otherwise made up of radiate spicules, of the British 

 species called by Dr. Bowerbank u Leucogypsia Gossei " 

 (No. 1, vol. i. pi. xxvi. figs. 349, 350) = Leucandra Gossei, 

 liackel (No. 2, Atlas, Taf. xxxii. fig. 2 ? /), also in Hackel's 

 Leucandra bomba (No. 2, Taf. xxxviii. fig. 4) ; while a slight 

 resemblance to" the undulating form of Stellispongia variabilis 

 may be seen in his Ascandra reticulum (No. 2, Taf. xiv. 

 fig. 4,/*), and Leucortis pulvinar, var. indica (No. 2, Taf. 



. figs. 16-18), respectively. 



On the other hand, precisely the same form of monactinellid 

 spicule as that in Pharetrospongia Strahani, and no other, 

 may be seen to form precisely the same kind of fibre in existing 

 species of Renierse, as Prof. Sollas has shown in his faithful 

 account of this sponge (No. 5, pi. xi. fig. 12), where, of course, 

 the mineral composition is siliceous. There is no sheath here 

 as in Sestrostomella and Scyphia cylindrica, no colossal axial 

 spicules, triradiates, or " pitchfork-like spicules/' but one 

 single form of monactinellid spicules, which, u dove-tailed " 

 into each other with great plurality, form a round spiculo- 

 fibre similar to that of similar spicules in a vast number of 

 siliceous sponges of the present day. ' If, then, these sponges 

 are to be considered fossil Calcispongise, some other means 



